1. Field of the Invention
The present invention relates to butanol compositions for fuel blending and fuel blends comprising such compositions. The compositions and fuel blends of the invention have desirable performance characteristics and can serve as alternatives to ethanol-containing fuels. The present invention also relates to methods for producing such butanol compositions and fuel blends.
2. Background of the Invention
Global demand for liquid transportation fuel is projected to strain the ability to meet certain environmentally driven goals, for example, the conservation of oil reserves. Such demand has driven the development of technology which allows utilization of renewable resources to mitigate the depletion of oil reserves. This invention addresses the need for improved alternative fuel compositions and processes that allow for the conservation of oil reserves. Such compositions and processes would satisfy both fuel demands and environmental concerns.
Fuels, and in particular gasolines, are typically required to meet certain performance parameters or standards. Such standards are implemented for proper operation of engines or other fuel combustion apparatuses, or for other reasons such as environmental management. Examples of performance parameters include, but are not limited to, vapor pressure (e.g., Reid vapor pressure), sulfur content, oxygen content, aromatic hydrocarbon content, benzene content, olefin content, temperature at which 90% of the fuel is distilled (T90), temperature at which 50% of the fuel is distilled (T50), temperature at which 10% of the fuel is distilled (T10), octane ratings, anti-knock index, ASTM Driveability Index, combustion properties, and emissions performance parameters.
Standards for gasolines for sale within much of the United States are set forth by the American Society for Testing and Materials (ASTM), in particular in ASTM Standard Specification Number D-4814 (“ASTM D-4814”), which is incorporated by reference herein. Additional federal and state regulations supplement this standard. The specifications for gasolines set forth in ASTM D-4814 vary based on a number of parameters affecting volatility and combustion such as weather, season, geographic location and altitude. For this reason, gasolines produced in accordance with ASTM D-4814 are broken into vapor pressure/distillation classes AA, A, B, C, D and E, and vapor lock protection classes 1, 2, 3, 4, 5 and 6, each class having a set of specifications describing gasolines meeting the requirements of the respective classes. These specifications also set forth test methods for determining the parameters in the specification.
Ethanol is routinely blended with both finished gasoline and gasoline subgrades (e.g., blendstocks for oxygenate blending, or BOB) to make fuel blends. The blending process can occur at truck loading terminals where gasoline or a gasoline subgrade and ethanol are combined from separate storage tanks into the fuel product by commingling the streams during loading onto the tanker trucks for transportation to service stations. The blending process can be accomplished sequentially (i.e., first one component is loaded, followed by the other) or simultaneously by real-time stream blenders. Some such blending processes are commonly referred to as splash-blending.
Butanol is an important industrial chemical that is also suitable for use in fuel blends. The use of butanol in fuel blends has several advantages over ethanol. For example, because butanol has an energy content closer to that of gasoline, consumers face less of a compromise on fuel economy with butanol fuels. Also, butanol has a low vapor pressure, meaning that it can be easily added to conventional gasoline. Butanol can be used in higher blend concentrations than ethanol without requiring especially adapted vehicles. Butanol fuel blends are also less susceptible to separation in the presence of water than ethanol fuel blends. Further, butanol's chemical properties allow it to be blended at least 16% by volume in gasoline, thereby displacing more gasoline per gallon of fuel consumed than the standard 10% by volume ethanol blend.
Because of the different physical properties of butanol and ethanol, butanol cannot always be substituted directly for ethanol in fuel blends, particularly at relatively higher butanol concentrations (e.g., 20 vol. % or greater). At such concentrations, the relatively higher boiling point of butanol can alter the fuel blend's evaporation characteristics and lead to cold-start and warm-up driveability problems in vehicles. Additionally, gasoline blendstocks (BOBs) and subgrades that have been formulated for ethanol gasoline blends are not fully compatable with butanol. In this respect, one cannot simply substitute butanol for ethanol for blending with blendstocks or subgrades that have been formulated for a particular ethanol percentage. Prior to this application, if one were to substitute butanol for ethanol by blending butanol into a blendstock or subgrade that was formulated for ethanol, the resulting gasoline would not meet the requisite regulatory requirements for performance. In other words, such a substitution would result in a gasoline blend that is off-specification, and therefore, would be unmarketable.
One aspect of this invention provides compositions having butanol and other materials described herein useful in fuel blending. Such compositions can directly replace ethanol in fuel blends. For example, the instant butanol compositions can be used in gasoline blendstocks for oxygen blending (gasoline, BOB) or gasoline subgrades (e.g., butanol splash-blending compositions), including blendstocks and subgrades that have been formulated for ethanol. The invention also provides compositions containing butanol and other materials described herein that mollify the negative impact of relatively high butanol concentrations on the performance properties of a fuel blend (e.g., volatility). Because the compositions of the invention can be used as a substitute for ethanol directly at a terminal, they offer at least the same flexibility as ethanol in creating fuel blends. In this respect, the compositions herein allow fuel producers to use the same gasoline blendstocks and subgrades for butanol blends and ethanol blends, even if the blendstocks and subgrades were formulated for ethanol blends. Before, fuel producers could only use blendstocks and subgrades formulated for ethanol with ethanol. This novel advancement provides fuel producers with greater choices for fuel production and blends, without having to get or produce different or modified blendstocks and subgrades. Additionally, the present application allows terminals that blend ethanol with gasoline or gasoline subgrades, to produce fuels by conveniently switching from blending with ethanol to blending with butanol, without requiring exhaustion of the ethanol inventory, having to provide or produce different blendstocks or subgrades, or having to provide additional facilities for handling butanol blending. In this respect, the present application allows terminals that do not have a convenient way to handle butanol blending to still produce butanol-containing fuels. The present application also allows terminals, including, but not limited to truck terminals, to produce butanol gasoline blends using gasoline blendstocks, subgrades, or mixtures thereof formulated for ethanol at the terminal, without any additional modifications or equipment. Moreover, the present application allows existing ethanol production plants to retrofit the facility for the production of biobutanol, preferably in a manner that economically uses equipment that is already in place, so as to avoid costly equipment modifications or additions. Furthermore, the present invention provides methods for producing butanol compositions for fuel blending and fuel blends at a location where butanol is already produced using equipment which is already in place and available.
This invention addresses the need for improved alternative fuels that meet or exceed performance standards and parameters of ethanol-based fuel blends by providing compositions containing butanol and other materials described herein. Such compositions can directly replace or supplement ethanol in fuel blends. Thus, such compositions can satisfy both fuel demands and environmental concerns while providing acceptable performance standards and parameters. The present invention satisfies these and other needs, and provides further related advantages, as will be made apparent by the description of the embodiments that follow.